Tumor is a major disease jeopardizing human health, and the global number of annual deaths due to malignant tumor is the second largest among all diseases. Research on anti-tumor drugs has been drawing close attention all around the world. Traditional chemotherapy drugs may block cell division non-specifically or cause cell death directly, thus destroying human normal cells while killing tumor cells. With thorough understanding of the mechanism behind formation and development of tumor, the development of novel drugs with high efficacy, low toxicity and high specificity by targeting essential enzymes in the signaling pathway of tumor cell has become an important trend in current researches of anti-tumor drugs.
Among various targets of anti-tumor drugs, protein tyrosine kinase signaling pathway is closely related to the proliferation and differentiation of tumor cells. Interfering or blocking tyrosine kinase signaling pathway has become a focus of current researches and developments of anti-tumor drugs. Each year, a large number of studies are reported. A variety of tyrosine kinase inhibitors have come into the market, such as Gefitinib which is a tyrosine kinase inhibitor for treating lung cancer, Gleevec which is a tyrosine kinase inhibitor for treating chronic myelogenous leukemia, and Sunitinib for treating advanced renal cell carcinoma, etc. They can act on multiple targets including epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor (VEGFR), etc. More other tyrosine kinase inhibitors under developments have entered into different stages of clinical studies.
Anti-tumor drug Gefitinib (Iressa) is a tyrosine kinase inhibitor developed by AstraZeneca, UK. It was approved for use in advanced or metastatic non-small cell lung cancer (NSCLC) in the United States in 2003, and it was approved for marketing in China in 2005. Clinical studies were carried out in five Chinese clinical study sites, to assess the objective response rate of Gefitinib tablet 250 mg/day in NSCLC patients who have received chemotherapy previously. A total of 159 subjects received at least one dose of Gefitinib tablet 250 mg. The results showed that the objective response rate was 27.0% (according to Gefitinib's instruction, baike.soso.com/v8292080.htm). This indicated that the drug resulted in a low efficacy. Therefore, keeping on looking for efficient tyrosine kinase inhibitors has important practical significance.